🎨 Palette: Accessibility improvements for form labels, dropzone and progress bar

[Nawayisus]

🎨 Palette: Accessibility improvements for form labels, dropzone and progress bar

💡 What: Added for attributes to form labels, made the file upload dropzone keyboard accessible (tabindex="0", role="button", Space/Enter support), added aria-live="polite" to status text, and dynamically updated aria-valuenow on the progress bar.
🎯 Why: Makes the core application workflow (selecting settings and uploading files) discoverable and usable for screen reader users and keyboard-only navigators.
♿ Accessibility: Improves ARIA attributes, semantic structure, and native keyboard interaction.

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PR created automatically by Jules for task 7872388224479310012 started by @Nawayisus

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